Conventional tap position indicators are implemented as electromechanical devices. Conventional implementations of tap position indicators use mechanical components to indicate the tap position on a circular dial. Gears, bearings, and other mechanical components are used to display the present, minimum and maximum tap position values. In one such implementation, mechanical means are used to track the maximum and minimum ("drag hands") positions. The operator resets the drag-hand readings using a control panel switch, which activates a solenoid to return the drag-hands to the current tap position. The solenoid also includes moving parts and like the display mechanism is subject to reliability and longevity problems.
The reliability and longevity problems of conventional tap position indicators make them costly to maintain and necessitate frequent replacement. Additionally, conventional electromechanical tap position indicators are costly to manufacture.
Electromechanical tap monitoring systems are described in U.S. Pat. Nos. 5,428,551, 5,619,121 and 5,633,580.